An analysis of rabbit vitreous collagen

Immunohistochemical studies of the extracellular matrix in the condylar cartilage of the human fetal mandible: collagens and noncollagenous proteins

This study provides data concerning the cells and their extracellular matrix in prenatal human mandibular condylar cartilage. The latter cartilage represents a secondary type of cartilage since it develops late in the morphogenesis of the craniofacial skeleton. The cartilage of the mandibular condyle is actively involved in endochondral ossification, thus showing all the phases of cartilage growth, maturation, and mineralization that precedes de novo bone formation. The present study focused on the localization and distribution of the major macromolecules that are normally encountered in cartilage and bone, including collagens, proteoglycans, fibronectin, osteonectin, osteocalcin, alkaline phosphatase, and anchorin CII. It became clear that the mineralized zone of the cartilage already contained bone-specific antigens; thus the above zone might serve as an essential propagative predecessor in the ossification process.

Corneal stromal fibroblasts from adult rabbits retain the capacity to deposit an orthogonal matrix

Stromal fibroblasts from the adult rabbit cornea were propagated in vitro, then injected into the vitreous compartment of normal rabbit eyes. In this environment the stromal cells deposited a matrix of imperfect orthogonal collagenous lamellae resembling normal corneal stroma. Extracellular matrices were also secreted by other ocular and nonocular cell types intravitreally, but no orthogonal regions were observed. The vitreous appears to provide some of the physical and humoral factors required to permit adult corneal fibroblasts to secrete a stroma-like matrix in the absence of embryonic tissue influences.

Studies on a distinct fraction of bovine vitreous body collagen

We were able to separate pepsin-solubilized collagen of the bovine vitreous body into three distinct fractions by differential salt precipitation with 0.5 M acetic acid containing 0.7 M, 1.2 M, and 2.0 M NaCl, respectively. The 0.7 M NaCl fraction showed an electrophoretic mobility in polyacrylamide gel identical to that of type II collagen, CNBr-derived peptides very similar to type II collagen CNBr-peptides, and a reaggregation behaviour closely related to type II collagen as observed by electron microscopy. Therefore, the fibres of the bovine vitreous body appear to contain a mixture of a collagen very similar to type II collagen precipitable in the presence of 0.7 M NaCl, at least two different collagen types that can be precipitated at 1.2 M, and 2.0 M NaCl concentrations that have not been identified previously.

A new look at vitreous-humour collagen

The collagens of bovine vitreous-humour and nasal-septum cartilage have been extracted, fractionated and compared. Both tissues show the same heterogeneity of collagen types, consisting of type II, 1 alpha, 2 alpha, 3 alpha and C-PS collagens. The type II collagen of the vitreous humour was significantly more hydroxylated both in the lysine and proline residues than was that of cartilage. C-PS1 collagen, together with higher-Mr forms were present in the vitreous humour, but the higher-Mr forms were not seen in cartilage. Both C-PS1 and C-PS2 were present in vitreous humour and cartilage, but vitreous humour contained three times more of these collagens than did cartilage. Despite the difference in amount, the molar ratio C-PS1/C-PS2 was approx. 1 in both tissues, suggesting that they are components of a larger molecule. The 1 alpha, 2 alpha, 3 alpha collagens were present in the same concentration in both tissues. These three chains co-precipitated on dialysis against phosphate-buffered saline, pH 7.2, in a manner analogous to type V collagen.

Biosynthesis and processing of collagens in different cartilaginous tissues

The distribution, structure, and biosynthesis of various collagen types have been studied in growth and structural cartilage from young rabbits. The major collagen of cartilage is alpha 1(II); however, all cartilage matrix also contains 1 alpha, 2 alpha, 3 alpha (Type Cm), as well as a high molecular weight disulfide-linked collagen (Type M). Cartilage fragments in organ culture demonstrate synthesis of precursors of collagen alpha chains and processing to their final forms. Although Type Cm collagen is present in the same proportion in the matrix of growth and structural cartilage, in vitro radiolabeling of rabbit cartilage showed that only growth cartilage is capable of actively synthesizing Type Cm, except in the newborn period when synthesis of Type Cm does occur in structural cartilage. A low molecular weight collagen (designated G collagen) is synthesized in vitro by growth cartilage but not by structural or articular cartilage. Preferential distribution of these minor collagens in growth cartilage suggests a role in development during normal cartilage growth.